Smart Antenna With Multiple Round Selection

ABSTRACT

A smart antenna system for communicating wireless signals between a mobile device and a plurality of fixed base stations using different channels and beams. The system comprises a control subsystem, a radio transceiver and an antenna subsystem, providing a plurality of beams. Each beam has a main lobe, one or more nulls, and one or more lateral and back lobes with at least some attenuation, so as to reduce interference. The system performs scanning of different combinations of base stations, channels and beams using one or more test links established with one or more of the fixed base stations. The test links use at least some of the different channels and the different beams, select a first combination of base station, channel and beam based on the scanning, and establish a first operating link for transmitting a wireless signal to the selected base station using the selected channel and beam.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/970,059, filed Aug. 19, 2013, which is a continuation-in-part of U.S.application Ser. No. 13/644,852, filed Oct. 4, 2012, now issued as U.S.Pat. No. 8,548,516, which is hereby incorporated by reference herein inits entirety.

FIELD OF THE INVENTION

This invention is directed towards antenna systems for mobile devices.

BACKGROUND OF THE INVENTION

Wireless communication is extensively used in mobile or nomadicapplications.

In a typical mobile/nomadic application, a mobile or nomadic wirelessdevice or mobile station will try to establish a link with a fixed basestation, so as to transmit information to the base station. To achievecoverage of the desired area, multiple base-stations must be used. FIG.1 shows an example of a system used to support a mobile application.Mobile station 111 will try to establish a link with one of basestations 121 and 122, as it travels along path 131.

Typical solutions for mobile or nomadic wireless devices useomnidirectional antennas that are isotropic or have similar properties,for example gain, in all directions of interest.

While mobile/nomadic devices use omnidirectional antennas, strictseparation between base-stations covering adjacent areas is required toavoid harmful self-interference.

Separation can be achieved through:

-   -   Time, that is, the base stations do not transmit and receive at        the same time,    -   Frequency, that is, the base stations transmit and receive on        different frequencies, or    -   Code, that is, the base stations transmit and receive using        different codes.    -   All these methods reduce the total system capacity.

FIG. 2 shows an example of the coverage 403 for base-station 401 and thecoverage 404 for the base-station 402 when both base-stations use thesame frequency channel, and the three mobile/nomadic devices 406, 407and 408 use omnidirectional antennas. This assumes there are no othertime or code methods used to reduce interference between the twobase-stations 401 and 402. As can be seen, much of the area of interest405 is not adequately covered. Mobile device 406 receives coverage, thatis, it can establish an operating link with better than threshold signalquality from base station 401 in area 403. Similarly mobile device 407receives coverage from base station 402 in area 404. However, mobiledevice 408 cannot receive coverage from either base station 401 or 402because the signal quality is not good enough. This is because theomnidirectional antenna captures signals from the two base-stations 401and 402 and needs to be very close to one of them and very far from theother to obtain the needed signal quality.

In order to solve the problem shown in FIG. 2, there is a need for asystem that has omnidirectional coverage, but is able to focus on onesector so as to optimize signal quality to enable communications withthe highest reliability. Until now, systems have focused on optimizingsignal strength, which may not result in enabling communications withthe highest reliability.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, a smart antennasystem for communicating wireless signals between a mobile device and aplurality of fixed base stations using different channels and differentbeams, said smart antenna system comprising a control subsystem, a radiotransceiver and an antenna subsystem, said antenna subsystem providing aplurality of beams, each beam having a main lobe, one or more nulls, andone or more lateral and back lobes with at least some attenuation, so asto reduce interference; said control subsystem, radio transceiver andantenna subsystem coupled to each other to perform scanning of differentcombinations of base stations, channels and beams using one or more testlinks established with one or more of said fixed base stations, said oneor more test links using at least some of the different channels and thedifferent beams, select a first combination of base station, channel andbeam based on the scanning, and establish a first operating link fortransmitting a wireless signal to the selected base station using theselected channel and beam.

In accordance with another embodiment of the invention, a method ofcommunicating wireless signals between a mobile device and a pluralityof fixed base stations using different channels and a plurality ofbeams, each beam having a main lobe, one or more nulls, and one or morelateral and back lobes with at least some attenuation, so as to reduceinterference, said method comprising scanning different combinations ofbase stations, channels and beams using one or more test linksestablished with one or more of said fixed base stations, said one ormore test links using at least some of the different channels and thedifferent beams, selecting a first combination of base station, channeland beam based on the scanning, and establishing a first operating linkfor transmitting a wireless signal to the selected base station usingthe selected channel and beam.

In accordance with another embodiment of the invention, a method forcommunicating wireless signals between a mobile device and a pluralityof fixed base stations using different channels and a plurality ofbeams, each beam within the plurality of beams having a main lobe, oneor more nulls, and one or more lateral and back lobes with at least someattenuation, so as to reduce interference, said method comprisingestablishing a first operating link for transmitting a wireless signalusing a first combination of base station, channel and beam and if saidestablishment of first operating link on said first combination fails,further scanning different combinations of base stations, channels andbeams using one or more test links established with one or more of saiddifferent fixed base stations, said one or more test links using atleast some of the different channels and the different beams, selectinga second combination of base station, channel and beam based on thescanning, and establishing a second operating link for transmitting awireless signal to the selected base station using a second combinationof base station, channel and beam.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings.

FIG. 1 shows an example of a system used to support a mobileapplication.

FIG. 2 shows example coverage of a given area for a mobile/nomadicdevice or station with an omnidirectional antenna.

FIG. 3 shows a smart antenna system.

FIG. 4 shows a radiation pattern for beam 200.

FIG. 5 shows an example radiation pattern for arrangement 300.

FIG. 6 shows a flowchart of the process when the smart antenna system100 becomes active.

FIG. 6A shows one embodiment for determining the operating channel andthe best-performing beam from a candidate set of channels and beams.

FIG. 6B is the flowchart of the process for another embodiment when thesmart antenna system 100 becomes active.

FIG. 6C shows a sequence of steps for the tracking process.

FIG. 7 shows an illustrative example of the advantage of makingselections of base station, operating channel and beam based on signalquality over signal strength.

FIG. 8 shows example coverage of a given area for a mobile/nomadicdevice or station with a smart antenna with the same base stations andthe same area of interest as in FIG. 2.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Although the invention will be described in connection with certainpreferred embodiments, it will be understood that the invention is notlimited to those particular embodiments. On the contrary, the inventionis intended to cover all alternatives, modifications, and equivalentarrangements as may be included within the spirit and scope of theinvention as defined by the appended claims.

Turning now to the drawings and referring first to FIG. 3, FIG. 3 showsa smart antenna system 100 consisting of radio transceiver 101 totransmit over a wireless link; an antenna subsystem 102; and a controlsubsystem 103. Information can be passed between the radio transceiver101, antenna subsystem 102 and control subsystem 103. For example, thecontrol subsystem 103 can receive information, including, but notlimited to wireless link quality information; and other information suchas base station operating capacity and base station load/utilization;from either or both of the radio transceiver 101 and the antennasubsystem 102. The control subsystem 103 can process this informationand command either or both of the radio transceiver 101 and antennasubsystem 102 accordingly. The smart antenna system 100 is designed tobe installed in, for example, a mobile/nomadic device or station whichestablishes a wireless link to a base station.

The radio transceiver 101 performs several different functions,including but not limited to, for example, transmitting and receivinginformation on the available operating channels; obtaining data tocompute signal quality measures such as signal to noise ratio (SNR) andsignal to interference and noise ratio (SINR); and computing thesemeasures either by itself or together with the control subsystem 103. Inone embodiment, the operating channel to be used for transmitting andreceiving is set by the control subsystem 103. The radio transceiver cantransmit on more than one channel. This allows the smart antenna systemto have “background” operation. For example, while transmitting andreceiving on a channel used in a current operating link in theforeground, the control subsystem 103 can direct the radio transceiver101 to transmit and receive on other channels used in, for example, testlinks which have been set up in the background.

The antenna subsystem 102 provides multiple beams that can be selectedby the control subsystem 103. The multiple beams can be produced byindependent antennas, by beam-steering or by beam-forming. Thesetechniques are well known to one having skill in the art.

Each beam provides nulls (directions in which signal is stronglyattenuated) that can be used to eliminate interference. FIG. 4 shows anexample radiation pattern of such a beam 200, where the main lobe 201 ofthe beam covers the 90° sector between lines 201-A and 201-B, while thelateral lobes 202 and 203 provide some attenuation and the back-lobe 204provides very strong attenuation.

The sum of the coverage of all beams provides omnidirectional coverage.FIG. 5 shows an example radiation pattern for such an arrangement 300,where the beam 200 of FIG. 4, with only main lobe 201 shown forsimplicity, is repeated 8 times as beams 301-308 at 45° intervals for360° coverage. Beams 301-308 are overlapping to ensure low ripple inomnidirectional coverage. The ripple 310 is the difference betweenmaximum gain and the minimum gain obtainable using all available beams.

The ability of the antenna subsystem 102 to provide multiple beamsallows for “background” operation on other beams. This, together withthe ability of the radio transceiver 101, to transmit and receive onother channels, means that the control subsystem 103 can establish testlinks in the background on different channels and beams, to the channeland beam used by the current operating link running in the foreground.

The control subsystem 103 is the controller of the smart antenna system100. The control subsystem 103 commands, controls, co-ordinates andmanages the operation of the antenna subsystem 102 and radio transceiver101. As explained previously, the control subsystem 103 can receiveinformation, such as wireless link status from either or both of theradio transceiver 101 and the antenna subsystem 102. When link status isactive, the control subsystem 103 can collect information related to,for example, signal quality; and other information such as base stationoperating capacity and base station load/utilization; from the radiotransceiver 101, or both the radio transceiver 101 and antenna subsystem102.

The control subsystem 103 can process this collected information andsend commands and control instructions to either or both of the radiotransceiver 101 and antenna subsystem 102 accordingly.

As previously explained, the control subsystem 103 collects informationrelated to signal quality. Various measures of signal quality can thenbe calculated. These measures include signal to noise ratio (SNR),signal to interference and noise ratio (SINR), bit error rate (BER) andpacket error rate (PER). As explained previously, in one embodiment thecontrol subsystem 103 collects this information, and then together withthe radio transceiver 101 calculates measures such as SNR and SINR. Inanother embodiment, the radio transceiver 101 calculates these measureson its own. In a further embodiment, the control subsystem 103 togetherwith the radio transceiver calculates a signal quality score for eachbase station based on a function which takes in one or more of signalquality measures such as SNR, BER, PER and SINR as inputs, and producesthe score as the output. For example, in one embodiment the controlsubsystem 103 calculates a weighted average based on SNR and SINR. Inanother embodiment, a weighted average is first calculated, thencompared against a threshold, and used to calculate a performance score.The control subsystem 103 can store also store historical signal qualityinformation, and other information for future use.

In one embodiment, the control subsystem 103 is an independent module.In another embodiment, the control subsystem 103 is integrated with theother radio transceiver 101 control functions. The control subsystem 103can be implemented in hardware, software, or some combination ofhardware and software. In another embodiment, the control subsystem 103is installed as software on, for example, the radio transceiver 101.

When the smart antenna system becomes active, for example, when it is:

powered up;

returned from sleep; or

turned active by the user;

the control subsystem 103 then performs scanning of combinations of basestations, channels and beams, that is, it establishes test links to basestations with different channels and beams using the radio transceiver101 and the antenna subsystem 102, and performs analysis of resultsobtained from these test links to select the best combination of basestation, channel and beam.

FIG. 6 shows a flowchart of the process when the smart antenna system100 becomes active. In optional step 601, the control subsystem 103selects a subset of the available beams and channels before thecommencement of the scanning process, and then performs scanning usingthe selected subset. In one embodiment, control subsystem 103 selectsthe subset based on historical signal quality. As previously explained,signal quality can be measured by, for example, one of SNR, BER, PER andSINR. As explained previously, in one embodiment the control subsystem103 together with the radio transceiver 101 calculates measures such asSNR and SINR. In another embodiment, the radio transceiver 101calculates these measures on its own. In a further embodiment, thecontrol subsystem 103 together with the radio transceiver 101 calculatesa signal quality score for each base station based on a function whichtakes in one or more of signal quality measures such as SNR BER, PER andSINR as inputs, and produces the score as the output. For example, inone embodiment the control subsystem 103 calculates a weighted averagebased on SNR BER, PER and SINR. In another embodiment, a weightedaverage is first calculated, then compared against a threshold, and usedto calculate a performance score.

In another embodiment, in optional step 601, the control subsystem 103uses geo-location information, for example, the location of themobile/nomadic device relative to the base-stations, to select thesubset of the available channels and beams. In yet another embodiment,positional/motion information obtained, for example, from sensors in themobile/nomadic device are used by the control subsystem 103 in optionalstep 601 to select the subset of the available channels and beams.Examples of positional/motion information include velocity of thedevice, acceleration of the device, direction of travel of the device,orientation of the device, angular velocity of the device, angularacceleration of the device and altitude of device. In yet anotherembodiment, the subset of the available channels and beams is selectedby control subsystem 103 based on user input and instructions.

In yet another embodiment, the subset of the available channels andbeams is selected in optional step 601 based on at least one ofhistorical signal quality, geo-location information, userinput/instructions and positional/motion information.

In yet another embodiment, in optional step 601 the control subsystem103 uses the fact that the beams are overlapping to select a subset ofbeams to perform scanning

Steps 602-604 detail the scanning process. In step 602, the controlsubsystem 103 determines the best-performing combination of basestation, channel and beam. It does so by attempting to establishwireless test links to base stations, using a set of candidate channelsand beams comprising at least some of the one or more availablechannels, and some of the one or more available beams. In oneembodiment, the candidate set is all available channels and beams. Inanother embodiment, the candidate set is the subset of channels andbeams selected using one of the methods outlined above.

For each wireless test link that the control subsystem 103 successfullyestablishes with a base station, the control subsystem 103 collectsinformation relating to signal quality of the test link. As previouslyexplained, signal quality can be measured by SNR, BER, PER or SINR. Inanother embodiment, the control subsystem 103 uses the test link tocollect information including, but not limited to, base stationoperating capacity; and base station load/utilization. In a furtherembodiment, control subsystem 103 uses the test link to collectinformation on packet drop rate at the base station.

The control subsystem 103 then measures the performance for thecombination of base station, channel and beam. In one embodiment,performance is measured by signal quality. As previously explained,signal quality can be measured by SNR or SINR. In one embodiment thecontrol subsystem 103 together with the radio transceiver 101 calculatesSNR and SINR. In another embodiment, the radio transceiver 101calculates these measures on its own. In an alternative embodiment, thecontrol subsystem 103 together with the radio transceiver 101 furthercalculates a signal quality score based on a function which takes in oneor more of signal quality measures such as SNR and SINR as inputs, andproduces the score as the output. One example of such a function is aweighted average. Another example of such a function is where a weightedaverage is first calculated, then compared against a threshold, and usedto calculate a performance score.

In another embodiment, performance can be measured by calculating ascore for each combination based on a function which takes in one ormore of signal quality measures such as SNR and SINR; base stationoperating capacity; and base station load/utilization as inputs, andproduces the score as an output. For example, in one embodiment, thecontrol subsystem 103 calculates a weighted average based on SINR, basestation operating capacity; and base station load/utilization; andselects the base station with the best weighted average. In anotherembodiment, the control subsystem 103 first calculates the weightedaverage, then compares against a threshold, and uses the comparison tocalculate a final performance score. In a further embodiment, if basestation load is used as an input, then different estimates of basestation load can be used. In one embodiment, control subsystem 103 usesthe current load as an estimate of base station load. In anotherembodiment, control subsystem 103 uses the estimated final load of thebase station, that is, the load assuming that the traffic through thebase station is the sum of the current traffic through the base stationand the anticipated traffic to and from the mobile device sent throughthe base station. In yet another embodiment, the control subsystemobtains packet drop rate information from the base station, and usesthis obtained information to estimate the base station load.

FIG. 6A shows one embodiment to perform step 602 for a candidate set ofchannels and beams. In FIG. 6A, control subsystem 103 scans all channelsin the candidate set, and for each channel, all available beams in thecandidate set. In step 620, control subsystem 103 selects a firstchannel and a first beam from the candidate set. In step 621, controlsubsystem 103 attempts to establish a test link to a base station usingthe first channel and the first beam in the candidate set. If this issuccessful, (step 622) then in step 623 the control subsystem 103records performance for every base station, channel and beam for which atest link is successfully established.

In step 624, the control subsystem 103 checks to see if all beams havebeen used. If not, then, in step 625, the control subsystem 103 selectsthe next beam in the candidate set and returns to step 621. If all beamshave been used, then in step 626 the control subsystem 103 checks to seeif all channels have been used. If not, then in step 627, the controlsubsystem selects the next channel in the candidate set and returns tostep 621. If all channels have been used, the control subsystem 103 thenmoves to step 603.

In another embodiment in step 602, the control subsystem 103 scans beamsin the candidate set, and for each beam, it scans all channels in thecandidate set.

Once this is complete, then in step 603 the control subsystem 103 buildsa list showing performance for all combinations of base station, channeland beam.

In step 604 the control subsystem 103 selects the best performingcombination of base-station, channel and beam based on the informationit collected in steps 602 and 603. In one embodiment, selection isperformed using a multiple round process, wherein each round has acorresponding criterion. In this multiple round process, there is atleast one initial round followed by a final round. In each initialround, a corresponding portion of the combinations entered into theround is selected based on the criterion. This corresponding portioncomprises the best combination, and any other combinations fallingwithin a defined margin of the best combination. The correspondingportion is then entered into the following round. In the final round,the best combination is selected from the portion entered into the finalround. If during any initial round the corresponding portion onlycomprises one combination, then the process is ended and the singlecombination is selected.

For example, in a three-round process, the first and second rounds areinitial rounds, and the third round is the final round. In the firstround, combinations are ranked according to the first criterioncorresponding to the first round. A first portion comprising the bestcombination and all combinations within a first defined margin areselected. The first portion is then entered into the second round. Inthe second round, the combinations within the first portion are rankedaccording to the second criterion corresponding to the second round. Asecond portion comprising the best combination and all combinationswithin a second defined margin are selected. This continues until thefinal round wherein the best combination is selected. Example criteriainclude signal quality, signal strength, base station capacity and basestation load.

A further example is provided. In one embodiment, a two-round process isused. The first criterion corresponding to the first round is signalquality. Then, in the first round, signal quality for each combinationis measured using, for example, one or more of SNR, SINR, BER and PER;or a signal quality score as previously described. The combinations arethen ranked in descending order. Then, a first portion of thecombinations comprising the best combination and the combinations withina first defined margin from the best combination are selected for entryinto the next round. For example, if rankings are based on SINR, thecombination with the best SINR is chosen. Then, a first portion ofcombinations comprising those combinations within a first defined marginof N dB is chosen for entry into the next round. For example, if thebest combination has an SINR of 20 dB and the defined margin is 1 dB,then a first portion of combinations comprising all the combinationswith SINR between 19 and 20 dB are chosen for entry into the secondround.

In the second round, the corresponding second criterion is used to rankthe combinations within the first portion. For example, if the secondcriterion is signal strength, then the combinations within the firstportion are ranked in order of signal strength. Then the combinationwith the best signal strength is chosen.

Another example of a two round process is explained. In this example,the first criterion corresponding to the first round is base stationload. The first defined margin is, for example, 10%. The secondcriterion corresponding to the second round is signal strength. Then inthe first round, the first portion comprises the best combination andall combinations within 10% of the best combination. In the secondround, all combinations within the first portion are ranked based onsignal strength. The combination with the best signal strength ischosen. In another example, the first criterion is base station load andthe second criterion is signal quality.

At the end of the scanning process, in step 605, the control subsystem103 then establishes an operating link to the selected base-stationusing the selected operating channel and beam Communication over theoperating link is carried out in step 606. In a further embodiment, ifthe operating link is not successfully established in step 605, then thecontrol subsystem 103 establishes an operating link to the next bestcombination of base station, operating channel and beam, andcommunication over the operating link is carried out in step 606.

In one embodiment, as shown in FIG. 6B, in step 610, when the smartantenna system 100 becomes active, the control subsystem 103 configuresthe radio transceiver 101 first, and then the antenna subsystem 102 toconnect with the base station and establish an operating link on thechannel and with the beam on which an operating link was lastestablished. If operating link establishment fails (step 610A), thencontrol subsystem 103 performs steps 612-616, which are similar to steps602-606 described above. In one embodiment, similar to as describedpreviously for step 601, control subsystem 103 may optionally performstep 611, which is selecting a subset of the available channels andbeams for the candidate set in step 612.

In one embodiment, after the operating link is established the basestation, channel and beam selection remain fixed until the operatinglink is lost. Once the operating link is lost, the control subsystem 103performs steps 602-606 of FIG. 6. In one embodiment, similar to asdescribed previously, control subsystem 103 additionally performs step601.

In another embodiment, after the operating link is established, thecontrol subsystem 103 performs tracking, that is, the control subsystem103 continues to search for a better combination of base station,channel and beam than the currently selected combination of basestation, operating channel and beam. In one embodiment, the controlsubsystem 103 performs tracking in the background; while communicationover the currently established operating link is ongoing.

FIG. 6C shows a sequence of steps involved in tracking

In a further embodiment, the control subsystem 103 optionally performsstep 631 of FIG. 6, that is, it selects a new subset of channels andbeams to be used in the tracking process using at least one of signalquality, geo-location and positional/motion information as outlinedabove.

In another embodiment, in step 631, positional/motion information,examples of which have been previously detailed, can be used togetherwith geo-location information of the device to predict the path of thedevice, and orientation of the device along this predicted path. Basedon this predicted path/orientation and other information such asgeo-location information of the base stations; subsets of the basestations, beams and channels which are likely to provide better links inthe future can be pre-loaded for tracking. In another embodiment,predicted path and orientation are calculated by a subsystem external tothe smart antenna, and this information is communicated to the smartantenna to be pre-loaded for the tracking process.

In step 632, the control subsystem 103 determines performance for allcombinations of base station, channel and beam other than the currentlyselected combination. In one embodiment, similar to step 602, it does soby using a candidate set of channels and beams to establish test linksto base stations. In one embodiment, the candidate set is the subset ofbeams and channels previously selected in step 601 of FIG. 6. In anotherembodiment, the candidate set is the subset of beams and channelsselected in optional step 631. In yet another embodiment, the candidateset is the set of all available channels and beams. In one embodiment,performance is determined using the multiple round process describedearlier.

In one embodiment, in step 632 the control subsystem 103 performs steps620-627 of FIG. 6A for all combinations of base station, channel andbeam other than the currently selected combination.

In another embodiment, in step 632, control subsystem 103 searches for abetter beam by testing the performance of other beams while theoperating link is running on the currently selected beam. In oneembodiment, control subsystem 103 performs searching by periodicallyinstructing the antenna subsystem 102 to switch between the currentlyselected beam and its neighbors to detect if any of the neighboringbeams offer a better signal quality. This switching can be carried out,for example, during a period between data transmissions such as forexample, a gap between packets or bursts of packets. In anotherembodiment, these gaps or periods are inserted between datatransmissions to specifically allow such switching to occur.

In one embodiment, the control subsystem 103 tests the signal quality onthe neighboring beam using normal data packets on the neighboring beam.In another embodiment, the control subsystem 103 instructs the antennasubsystem 102 to switch from the currently selected beam to aneighboring beam during a period between data transmissions, and thentests the signal quality on the neighboring beam, using special channelsounding packets on the neighboring beam. Control subsystem 103 theninstructs the antenna subsystem 102 to switch back to the currentlyselected beam and resumes transmission of normal data packets. This isdone to ensure that the delivery of data packets is not affected in casethe signal quality on the neighboring beam is very poor.

In one embodiment, in optional step 633, the control subsystem 103builds a list showing performance for all combinations of base stations,channels and beams in step 633. As previously explained, performance maybe measured by signal quality or other measures, or a combination ofsignal quality and other measures. As explained previously, performancecan be measured using the multiple round process described earlier. Ashas also been previously explained, signal quality can be measured by,for example, SNR, SINR, or a score calculated from a function whichtakes in measures such as SNR and SINR as inputs, and produces the scoreas an output.

If, for example, using the list built in step 633, or otherwise, thecontrol subsystem 103 finds a better combination of base station,channel and beam than the currently selected combination of basestation, channel and beam (step 633A), then it moves to select thebetter combination in step 634. In another embodiment, the controlsubsystem 103 selects the better combination in step 634, only if thecontrol subsystem 103 determines that the improvement in signal qualitypersists for a predefined period.

If not, then control subsystem 103 continues searching for a bettercombination of base station, operating channel and beam. In oneembodiment, this involves selecting a new subset of available channelsand beams (step 631).

After the control subsystem 103 has selected the better combination instep 634, in step 635 the control subsystem 103 establishes a newoperating link to the selected base station using the new channel andbeam.

In step 636, communication over the newly established operating linkbegins.

In another embodiment, the control subsystem 103 searches for a standbycombination of base station, channel and beam, in case the currentoperating link fails. In one embodiment, the control subsystem 103periodically performs steps 631-633 of FIG. 6C in the background. If thecurrent operating link fails, then the control subsystem 103 selects thebest combination of base station, channel and beam identified;establishes a new operating link over this combination; and communicatesover this newly established operating link.

The process outlined above to select base station, operating channel andbeam based on signal quality offers advantages over making decisionsbased on signal strength. An illustrative example of these advantages isshown in FIG. 7. FIG. 7 which shows a mobile device 701 containing asmart antenna system, with wireless test links to base stations 702 and703. Device 701 determines that base station 702 provides better signalquality than base station 703. Device 701 then has to select a beam. Itdecides to select beam 712 over beam 711, for the following reason:Device 701 can establish a test link to base station 702 with eitherbeam 711 or 712 because it is in the area 713 in which the two beamsoverlap. The signal strength for base station 702 using beam 711 isstronger than beam 712 because base station 702 is closer to the centerof beam 711. However, if the control subsystem 103 selected beam 711,then it would have to contend with interference from base station 703,and therefore the SINR would be lower. Control subsystem 103 choosesbeam 712 because it offers lower interference, and consequently a bettersignal quality, than with beam 711.

FIG. 8 shows the coverage for the base stations 401 and 402 of FIG. 2but with the mobile/nomadic devices 511 and 513 using smart antennas.Compared to FIG. 2 the coverage 503 for the base-station 401 and thecoverage 504 for the base-station 402 are much larger, almost coveringthe entire area of interest 405. Mobile device 511 selects beam 512 thatprovides good signal strength from base station 401 and provides goodisolation from (rejection of) base station 402, which means good SINRand therefore signal quality. Similarly mobile device 513 selects beam514 that includes base station 402 but excludes base station 401.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationsmay be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

1. A smart antenna system for communicating wireless signals between amobile device and a plurality of fixed base stations using differentchannels and different beams, said smart antenna system comprising acontrol subsystem, a radio transceiver and an antenna subsystem, saidantenna subsystem providing a plurality of beams, each beam having amain lobe, one or more nulls, and one or more lateral and back lobeswith at least some attenuation, so as to reduce interference; saidcontrol subsystem, radio transceiver and antenna subsystem coupled toeach other to perform scanning of different combinations of basestations, channels and beams using one or more test links establishedwith one or more of said fixed base stations, said one or more testlinks using at least some of the different channels and the differentbeams, select a first combination of base station, channel and beambased on the scanning, and establish a first operating link fortransmitting a wireless signal to the selected base station using theselected channel and beam.
 2. The smart antenna system of claim 1 inwhich said control subsystem selects a subset of channels and beams, andsaid scanning uses said selected subset of channels and beams.
 3. Thesmart antenna system of claim 1 in which said selecting of a firstcombination of a base station, channel and beam is based on at least oneof signal quality, base station operating capacity and base stationload.
 4. The smart antenna system of claim 1 wherein after establishingsaid first operating link, said control subsystem performs continuedscanning using one or more test links established with one or morecombinations of base stations, channels and beams; selects a secondcombination of base station, channel and beam based on the continuedscanning; and establishes a second operating link for transmitting awireless signal to the selected base station from said secondcombination, using selected channel and beam from said secondcombination.
 5. The smart antenna system of claim 4, in which saidselection of a second combination of base station, channel and beam iseffected in response to at least one of failure of said first operatinglink, and finding a better-performing combination of base station,channel and beam during continued scanning than said first combinationof base station, channel and beam used to establish said first operatinglink.
 6. The smart antenna system of claim 1, wherein if establishmentof said first operating link fails, the control subsystem selects asecond combination of base station, channel and beam based on thescanning, and establishes a second operating link, using said selectedsecond combination of base station, channel and beam.
 7. The smartantenna system of claim 4 in which said selecting of a secondcombination of a base station, channel and beam is based on at least oneof signal quality, base station operating capacity and base stationload.
 8. The smart antenna system of claim 3 wherein said selecting of afirst combination of a base station, channel and beam is based on signalquality, and further wherein said signal quality is measured using atleast one of SINR, SNR, BER and PER.
 9. The smart antenna system ofclaim 4, wherein said continued scanning is performed using specialchannel sounding packets.
 10. The smart antenna system of claim 1 inwhich said selecting of a first combination of a base station, channeland beam is based on a multiple round process, and wherein each round ofsaid multiple round process has a corresponding criterion.
 11. The smartantenna system of claim 10, wherein said multiple round processcomprises at least one initial round followed by a final round, whereineach of the at least one initial round has a corresponding definedmargin; and during each of the at least one initial round acorresponding portion is chosen for entry into the following round basedon the corresponding criterion, and said corresponding portioncomprising the best-performing combination based on the correspondingcriterion and one or more combinations with performances within thecorresponding defined margin of the performance of the best combination.12. The smart antenna system of claim 11, wherein the multiple roundprocess is a two-round process, the criterion corresponding to the firstround is signal quality, wherein said signal quality is measured usingat least one of SINR, SNR, BER and PER, and the criterion correspondingto the second round is signal strength.
 13. The smart antenna system ofclaim 11, wherein the multiple round process is a two-round process, thecriterion corresponding to the first round is base station load, and thecriterion corresponding to the second round is signal strength.
 14. Thesmart antenna system of claim 11, wherein the multiple round process isa two-round process, the criterion corresponding to the first round isbase station load, and the criterion corresponding to the second roundis signal quality, wherein said signal quality is measured using atleast one of SINR, SNR, BER and PER.
 15. The smart antenna system ofclaim 3 wherein said base station load is estimated based on one ofcurrent load, estimated final load of the base station, and packet droprate.
 16. A method of communicating wireless signals between a mobiledevice and a plurality of fixed base stations using different channelsand a plurality of beams, each beam having a main lobe, one or morenulls, and one or more lateral and back lobes with at least someattenuation, so as to reduce interference, said method comprisingscanning different combinations of base stations, channels and beamsusing one or more test links established with one or more of said fixedbase stations, said one or more test links using at least some of thedifferent channels and the different beams, selecting a firstcombination of base station, channel and beam based on the scanning, andestablishing a first operating link for transmitting a wireless signalto the selected base station using the selected channel and beam. 17.The method of claim 16, further comprising selecting a subset ofchannels and beams; and said scanning uses said selected subset ofchannels and beams.
 18. The method of claim 16 in which said selectingof a first combination of base station, channel and beam is based on oneof signal quality, base station operating capacity and base stationutilization.
 19. The method of claim 16 further including continuing,after establishing said first operating link, to scan using one or moretest links established with one or more combinations of base stations,channels and beams, selecting a second combination of base station,channel and beam based on the scanning, and establishing a secondoperating link for transmitting a wireless signal to the selected basestation from said second combination, using selected channel and beamfrom said second combination.
 20. The method of claim 19, in which saidselecting of second combination of base station, channel and beam iseffected in response to at least one of failure of said first operatinglink, and finding a better-performing combination of base station,channel and beam during scanning than said first combination of basestation, channel and beam used in establishing said first operatinglink.
 21. The method of claim 19 in which said selecting of a secondcombination of a base station, channel and beam is based on one ofsignal quality, base station operating capacity and base stationutilization.
 22. The method of claim 16 in which said selecting of afirst combination of a base station, channel and beam is based on amultiple round process, and wherein each round of said multiple roundprocess has a corresponding criterion.
 23. The method of claim 22,wherein said multiple round process comprises at least one initial roundfollowed by a final round, wherein each of the at least one initialround has a corresponding defined margin; and during each initial rounda corresponding portion is chosen for entry into the following roundbased on the corresponding criterion, and said corresponding portioncomprising the best-performing combination based on the correspondingcriterion and one or more combinations with performances within thecorresponding defined margin of the performance of the best combination.24. The method of claim 22, wherein the multiple round process is atwo-round process, the criterion corresponding to the first round issignal quality, wherein said signal quality is measured based on atleast one of SINR, SNR, BER and PER, and the criterion corresponding tothe second round is signal strength.
 25. The method of claim 22, whereinthe multiple round process is a two-round process, the criterioncorresponding to the first round is base station load, and the criterioncorresponding to the second round is signal strength.
 26. The method ofclaim 22, wherein the multiple round process is a two-round process, thecriterion corresponding to the first round is base station load, and thecriterion corresponding to the second round is signal quality, andwherein said signal quality is measured based on at least one of SINR,SNR, BER and PER.
 27. The method of claim 16, wherein if saidestablishing of first operating link on said first combination fails,further scanning different combinations of base stations, channels andbeams using one or more test links established with one or more of saiddifferent fixed base stations, said one or more test links using atleast some of the different channels and the different beams, selectinga second combination of base station, channel and beam based on thescanning, and establishing a second operating link for transmitting awireless signal to the selected base station using a second combinationof base station, channel and beam.
 28. The method of claim 18 whereinsaid selecting of a first combination of a base station, channel andbeam is based on signal quality, and further wherein said selecting isbased on at least one of SINR, SNR, BER and PER.
 29. The method of claim19, wherein said continued scanning is performed using special channelsounding packets.
 30. The method of claim 18, further comprisingestimating base station load based on one of current load, estimatedfinal load of the base station, and packet drop rate.